Oracle has provided built-in audit capabilities for many years and in the most recent versions, this auditing is very sophisticated. The Fine Grained Auditing (FGA) that you can use now can provide audits for all DML against a database, a schema or specific objects. FGA can also audit who was selecting data and not just who updated data. Oracle can also track who changed database objects (DDL, like alter table or compile procedure), what they did and when they did it.

The first thing to do is to activate audit which is disabled by default. To do so, use the command:

ALTER SYSTEM SET audit_trail=db SCOPE=SPFILE;

Then, you have to restart the database, using SHUTDOWN, and STARTUP to start it up again.

Login Tables used in AuditFND_LOGINS – holds information about users login to system, when and how long. This table holds one row for each login.FND_LOGIN_RESPONSIBILITIES – holds information about changes of responsibilities, when and how long being at each responsibility.
For each change this table holds one row with values that identify the user’s login session, the user’s current responsibility, and when the user is in the responsibilityFND_LOGIN_RESP_FORMS – holds information about using forms, when and how long.
This table holds one row for each form used in the same session with values that identify the user’s login session, current responsibility, when and how long using each form.

In order to see the user audit information, there are 5 reports (concurrent) that you can use:

Signon Audit Concurrent Request:Show concurrent requests audit information – the user who run this request, when, from which responsibility and form, for all concurrent requests run in the system.Signon Audit Forms:Show audit information about which user enter to which form, when and for how long.Signon Audit Responsibilities:Show audit information about which user choose which responsibility, when and how long he stayed in each responsibility.Signon Audit Unsuccessful Logins:Show audit information about unsuccessful logins to Oracle Applications.Signon Audit Users:Show audit information about who sign on, when and for how long.

Sign-On: Audit Level profile:

This profile can be set to one of the four possible values at site level,

What you need to do in order to enable it is:

NONE – no audit enabled (Default value)USER – audit user login to system, the logon time and the logoff time.RESPONSIBILITY – audit all the above + which responsibilities the user chose and how long he stayed in each responsibility.FORM – audit all the above + which forms the user used and how long he stayed in each form.

You can see online data using monitor screen for the users connected to system, which responsibility and form they are using and how long they are connected.
You can use this monitor from:
System Administrator responsibility -> security -> User -> Monitor.

To inform users aboutunsuccessful logins to their account, you can set the “Sign-On:Notification” profile to Yes.